Regenerative heat exchangers have disadvantages such as low heat transfer coefficient from the nozzle to the gas and high hydraulic resistance due to the design of the nozzles. Wire-mesh nozzles can eliminate these shortcomings of regenerators. Wire-mesh nozzles have low hydraulic resistance and large heat transfer surface.
The process of heat and mass transfer in a regenerative heat exchanger is considered. A series of numerical simulation experiments was performed.
Theoretically, the optimal configuration of the nozzle was calculated: a plain weave mesh with a wire diameter of 0.4 mm, a weaving step of 2 mm, and a step of placing nets of 1 mm. The operational modes for the regenerator are considered, taking into account the period for drying the nozzle from moisture and the maximum mass of water that can hold the nozzle without the formation of drops.
Given the condensation of moisture on the nozzle, the following assumptions are made:
There is no temperature and concentration inhomogeneity in the cross section of the regenerator channel;
The effect of thermal conductivity in the axial direction in contact between the nozzle elements on the temperature profile of the nozzle is insignificant;
The time over which the regenerator is operated between the nozzle drying periods is quite short, and the thickness of the condensate layer does not affect the hydrodynamic mode of the heat regeneration process and the value of the heat transfer coefficient.
The duration of the cooling and drying period depends on the humidity of the inlet air and the area of the nozzle. This is due to the need to prevent the accumulation of moisture in the device, which can lead to the reproduction of harmful bacteria and contamination of the nozzle.
In the SolidWorks Flow Simulation application, simulation experiments were performed for a regenerator model accounting for the influence of compressed air motion resulting from grouped location of the nozzle elements, and the results are shown in the figures.
Comparison of the results from analytical calculations and simulation experiments showed the efficiency of the mathematical model and the possibility of its use in the design calculation of regenerators.
Correlation dependences have been established to determine the heat transfer coefficient and hydraulic resistance depending on the hydrodynamic conditions. The mathematical and physical model taking into account the condensation of moisture on the nozzle has been specified. Calculations have been performed for the optimal nozzle made in the form of a plain weave mesh with a wire diameter of 0.4 mm, a weaving step of 2 mm, and a step of placing nets of 1 mm.
Parameters of the plain weave meshfor the nozzle of a regenerative heat exchanger
